

Valve employee Erik Johnson explained the engine's nomenclature on the Valve Developer Community: Carmack commented on his blog in 2004 that "there are still bits of early Quake code in Half-Life 2". Source distantly originates from the GoldSrc engine, itself a heavily modified version of John Carmack's Quake engine with some code from the Quake II engine. Updates to Source were released in incremental versions, with the engine being succeeded by Source 2 by the late 2010s. It debuted as the successor to GoldSrc in 2004 with the release of Counter-Strike: Source and Half-Life 2. Source is a 3D game engine developed by Valve.
